1. Field of the Invention
This invention relates to a breath-actuated device. In particular, the device is directed to what is typically referred to as an inhaler having an aerosol medication containing canister, which upon actuation releases a metered dose of medication to a patient.
2. Description of the Prior Art
There are a variety of inhalation devices which release aerosol medication, in a continuous spray or in a metered dose or predetermined amount of medication, directly into the patient""s mouth, nasal area or respiratory airways. Typically, these devices are actuated by the pressured actuation of the user""s fingers, button action, or other related manual techniques. Although some are activated by the inhaling action of the users, heretofore there are few simple, inexpensive and reliable breath actuated devices developed.
Metered dose aerosol canisters of the medicine to be inhaled into the mouth, nasal areas or respiratory airways are manufactured by a variety of pharmaceutical companies. Metered dose aerosols are much the same as non-metered aerosol except that when the valve is depressed, a continuous spray does not result but instead a predetermined measured spray releases delivering a fixed amount of medication. Examples of such metered dose inhalers are set forth in U.S. Pat. No. 5,544,647, issued Aug. 13, 1996 entitled xe2x80x9cMetered Dose Inhalerxe2x80x9d; and 5,622,163 issued Apr. 22, 1997 entitled xe2x80x9cCounter for Fluid Dispensersxe2x80x9d; and U.S. patent application Ser. No. 09/241,010 filed Feb. 1, 1999 entitled xe2x80x9cMetered Dose Inhaler Agitatorxe2x80x9d (commonly assigned), the disclosures of which are incorporated herein by reference. Devices of this type have proven to be very satisfactory, however, as with everything else, improved operation is desirable.
Aerosols used with manually actuated inhaler devices often incorporate ambient air with the volume of medication permitting a complete breath of air by the patient while inhaling the medication. Alternatively, aerosol medicines are also available in continuous spray, which continually spray as long as the valve or nozzle pin is depressed.
Proper use of these manual actuated devices requires that the spray be activated at the beginning of the inspiratory cycle, so that the medication is carried into the lungs rather than being deposited in the mouth or throat. If this actuation is not correctly coordinated with the inspiratory phase the metered dose may be deposited differently with each actuation and potentially compromise the therapeutics and safety of the product. A breath actuated device helps eliminate this problem by making the product easier to coordinate and more patient friendly, with predictable delivery and dispersion in the respiratory airways.
There are numerous factors leading to poor coordination ranging from the user""s inherent skills, associated with the geriatrics and pediatrics to patients with impaired physical facilities. Recognizing the need for correct and accurately delivered doses in the asthmatics, COPD patients and, as with other patients with other respiratory illnesses, a reliable breath activated device would improve the quality of life for these respiratory ill patients.
The present invention comprises a metered dose dispenser for aerosol medication contained in a housing having a mouthpiece for insertion into a patient""s mouth. A mechanical actuator mechanism is provided in cooperation with the canister, in its initial locked position, which upon inhalation by a patient causes the canister to dispense a metered dose of medication as a spray from the mouthpiece to the patient. The dose is established by a metering valve associated with the canister. A dwell means is provided which ensures complete discharge of the metered dose and subsequently, complete filling of the metering valve with the next dose after the dispensing.